Control for dual hydrostatic drive

ABSTRACT

MECHANISM FOR CONTROLLING TWO SEPARATE POWER OUTPUTS TOGETHER OR INDEPENDENTLY, INCLUDING A PAIR OF PLATES MOUNTED FOR ROTATION, A PAIR OF CONVERGING SLOTS IN EACH PLATE, A ROD EXTENDING THROUGH EACH PAIR OF CORRESPONDING   SLOTS IN THE PLATES AND TENSION SPRING MEANS CONNECTED BETWEEN THE PAIR OF RODS.

Sept. 20, 1971 J. P. HEGGEN 3,605,519

CONTROL FOR DUAL HYDROSTATIC DRIVE Filed Jan. 26. 1970 5 Sheets-Shoot 2FIG. 2

INVENTOR JOHN P. HEGGEN BY? l ATTORNEY p 1971 J. P. HEGGEN CONTROL FORDUAL HYDROSTATIC DRIVE Filed Jan. 26. 1970 5 Sheets-Shoot 5 l N VEN 'lOR JOHN P. HEGGEN ATTORNEY Sept 9 J. P. HEGGEN CONTROL FOR DUALHYDROSTATIC DRIVE &605.519

Filed Jan. 26, 1970 5 Sheets-Sheet 4 INVEN'I'OR JOHN P. HEGGEN ATTORNEYSept. 20, 1971 J. P. HEGGEN CONTROL FOR DUAL HYDROSTATIC DRIVE 5Sheets-Shut 5 Filed Jan. 26. 1970 INVENTOR JOHN P. HEGGEN ATTORNEYUnited States Patent 3,605,519 CONTROL FOR DUAL HYDROSTATIC DRIVE JohnP. Heggen, Lisbon, N. Dak., assignor to Clark Equpment Company FiledJan. 26, 1970, Ser. No. 5,459 Int. Cl. Gg 13/00 U.S. Cl. 74-480R 8Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The fieldof art to which this invention relates includes control Systems, andmore specifically mechanical control Systems for dual hydrostatictransmissions.

A highly maneuverable four-wheeled -vehicle can be provided by utilizingdifferential steering. That is, the Wheels on one side of the Vehiclecan be driven at velocities and directions of rotation independently ofthe Wheels on the other side of the Vehicle. An example of such Vehiclewhich has been extremely successful is disclosed in U.S. Pat. No.3,231,1l7, which issued on Jan. 25, 1966, in the names of C. E. Melroeand L J. Keller.

In the case Where two separate hydrostatic transmissions areincorporated in such a Vehicle, it is desirable to have the Controls foreach transmission operable together Without any lag, as well asindependently. otherwise, it is difiicult to steer the Vehicle,especially at high speed. Also, it is desirable to limit thediiferential between the velocities of the Wheels on opposite sides ofthe Vehicle.

It is, therefore, a principal object of my invention 'to provide asimple mechanism which connects two separate hydrostatic transmissionsfor operation together -without any lag, or independently.

SUMMARY OF THE INVENTION In Carrying out my invention in a preferredembodiment, I provide a pair of rotatable shafts to which a pair ofplates are fixed. Each plate has a pair of converging slots thereinWhich register with corresponding slots in the other plate. A rodextends through each pair of corresponding slots and at least onetension spring is connected between the rods.

The above and other objects, features and advantages of my inventionwill be more readily understood by persons skilled in the art when thedetailed description is considered together with the drawing.

DESCRIPTION OF THE DRAWING FIG. 1 shows a compact four-wheeled front endloader embodying my invention.

FIG. 2 is a schematic diagram of the power train and Controls for theloader shown in FIG. l,

FIG. 3 shows my novel control mechanism,

FIG. 4 is an enlarged view of a portion of the control mechanism of FIG.3,

FIG. 5 is a right end view of the mechanism shown in FIG. 4, and

FIG. 6 is a left end view of the mechanism shown in FIG. 4, and

FIG. 7 is a sectional view along the line 7-7 in FIG. 4.

Referring to FIGS. 1 and 2, the reference numeral 10 3,605,5l9 PatentedSept. 20, 1971 loader having a body 12 which is supported by a pair ofdrive Wheels 14 and 16 on one side thereof and a pair of drive *Wheels18 and 20 on the other side thereof. Loader 10 includes a bucket 22connected to a pair of boom arms 24 which are in turn pivotallyconnected to a pair of upright stanchions 26 located adjacent the rearof body 12. Located on body 12 is an operator's station 28 whichincludes a seat 30 and a pair of speed and direction control handles 32and 34.

Referring now specifically to FIG. 2, the drive train 36 for loader 10includes a prime mover 38 which preferably is an internal combustionengine which has the Crank shaft connected to a transfer gear case 40 toprovide two separate power outputs 42 and 44. Drive train 36 alsoincludes two separate hydrostatic transmission portions 46 and 48.

Hydrostatic transmission 46 includes a variable displacement pump 50which is drivingly connected to output 42. Pump 50 includes a swashplate (not shown) which is connected to a lever arm 58 so that movementof lever 58 Changes the angle of the swash plate, and thus the pumpoutput. Connected to pump 50 by conduits 54 and 56 is a fiuid motor 52.Motor 52 has a rotatable shaft 60 to which a pair of sprockets 62 and 64are fixed.

Sprocket 62 is drivingly connected to another sprocket 66 by means of anendless chain 68 which engages the teeth of both sprockets. Sprocket 66is fixed to a stub axlc 70 mounted on body 12 and to which Wheel 16 isconnected. Similarly, sprocket 64 drivingly engages another sprocket 72by means of an 'endless chain 74 which engages the teeth of bothsprockets. Sprocket 72 is fixed to a stub axle 76 which is mounted onbody 12 and to which Wheel 14 is connected.

Hydrostatic transmission 48 has a variable displacement pump 7,8drivingly connected to output 44 and a fixed displacement motor 80 whichis connected to pump 78 by means of fiuid conduits 82 and 84. Pump 78includes a swash plate (not shown) which is Connected to lever arm 86 sothat movement there changes the angle of the swash plate and motor 80includes a rotatable shaft 88 to WhCh a pair of sprockets 90 and 92 arefixed.

sprocket 90 is drivingly connected to another sprocket 94 by means of anendless chain 96 which engages the teeth of the sprockets. sprocket 94is fixed to a stub axle 98 which is mounted on body 12r and to whichWheel 20 is connected. Similarly, sprocket 92 is drivingly connected toanother sprocket 100 by means of an endless chain 102 which engages theteeth of these sprockets. Sprocket 100 is fixed to a stub axle 104 whichis connected to body 12 and to which Wheel 18 is connected.

'It will be noted that both hydrostatic transmission Systems 46 and 48are of the closed circuit type. While such Systems are termed closed, itis nevertheless conventional to provide means for supplying fiuid to theSystems to make up for loss through leakage, etc. 'I-Iowever, such aprovision has not been shown since it has no relation to 'my inventionand is conventional and Well-known in the art. Also, both s'ystems couldhave variable displacement motors, if desired, in addition to thevariable displacement pumps.

At this point it will be clear that Wheels 14 and 16 on one side of theVehicle are connected together for conjoint rotation in the samedirection and that Wheels 18 and 20 on the other side of the Vehicle areconnected together for conjoint rotation in the same direction. Now, itis possible to vary the direction and speed of rotation of the pairs ofWheels on the opposite sides of Vehicle 10 by actuating lever arms *58and 86 which changes the swash plate angle in pumps 50 and 78. Thus,Vehicle 10 can be steered by having the speed or direction ofrotadenotes generally a compact four-wheeled front end tion or both forthe pair of Wheels on one side of the Vehicle different from that on theWheels on the other side of the Vehicle.

Referring now also to FIG. 3, the angle of the swash plate for pump 50is Controlled by the operator through manipulation of control handle 32which is connected to a rotatable sleeve shaft 106. connected to sleeveshaft 106 is a lever arm 108 Which is connected to lever arm 58 by meansof linkage 110. Similarly, the operator manipulates control handle 34 tovary the angle of the swash plate for pump 78. Control handle 34 isconnected to a shaft fi112 which is journaled for rotation in a pair ofbearings 114 and 116 which are carried by brackets 111 8 and 120. Thesebracket are adapted to be mounted at appropriate locations on body 12 ofloader 10. Fixed to shaft 1.12 is a lever arm 122 which is connected bymeans of linkage 124 to lever arm 86 of motor 80.

Referring additionally to FIGS. 4,5, 6 and 7, shafts 106 and 112 areinterconnected by means of mechanism 126 which includes a plate 128fixed to shaft 106 and a plate 130 fixed to shaft 1.12. Plate 128 hasdisposed therein a pair of converging slots 132 and 134. Similarly,plate 130 has disposed therein a pair of converging slots 136 and 138which register with corresponding Ones of slots 132 and 134. Extendingthrough and movable in slots 132 and .136 is a rod 140. Likewiseextending through and movable in slots 13 4 and 138 is a rod 142. Rods1'40 and 142 are biased together by a pair of tension Springs 144 and146 which are connected between rods 140 and 142.

A pair of washers 148 carried by rod 140 and held in place by cotterkeys 150 serve to retain rod 140 in slots 132 and 136. Likewise, a pairof washers 152 carried by rod 142 and held in place by cotter keys 154serve to retain rod 142 in slots 113 4 and 138.

dt Will now be apparent that the bias of tension Springs 144 and 146tends to pull rods 140 and 142 together in their respective slots withthe result that plates 128 and 130 are connected for con joint rotation,and further that such conjoint rotation takes place without any lag fortension to be built up on Springs 142 and 146 since they already areunder tension. Also, by overcoming the bias of Springs 144 and 1146,plates 128 and 130 can be rotated independently of each other. Thus,movement of either control handle Causes, without lag, a correspondingmovement of both lever arms 58 and 86 which control the swash plates ofpumps '50 and 78. On the other hand, control handles 32 and 34 can beactuated independently by overriding the bias of springs 144 and 146with the result that swash plates of pumps 50 and 78 can be actuatedindependently of each Other.

It s desirable to have the swash plates of pumps 50 and 78 normallybiased to their Zero displacement positions. This is accomplished bycentering mechanism 156 which biases plates 130 and 132 to apredetermined position. Mechanism 156 includes a roller 158 connected toplate 128 and a roller 160 connected to plate -130: These rollers engagea generally V-shaped cam 162 which is pivotally connected to bracket 120by means of a sleeve shaft 164 carried by a rod 166 which extendsbetween two legs of braoket 120. Cam 162 is biased into engagement withrollers 158 and 160 by means of a compression spring &168 which isdisposed between cam 162 and a backing plate 170 which extends acrossbracket 120. T hus, regardless of which direction rollers 158 and 160move along cam 162, the bias of spring 168 will tend to return them tothe apex of the cam, and so tend to bring plates 128 and 130 back to apredetermined position.

Referring now specifically to 'FIG. 7, there is provided mechanism 172for limiting the relative rotation of plates 128 and x130, and hencerelative displacement of the swash plates of pumps 50 and 78. Mechanis'm172 includes a tube 174 fixed to rod 142, preferably by Welding and arod 176 which extends through tube 174 and is connected at one endthereof to rod 140 by Welding and which has a pair of look nuts 178threadably connected to the other end of rod 176 to serve as a stop withthe adjacent end of tube 174. Thus, by adjusting the clearance betweennuts 1 78 and tube 174 (the distance nuts 178 are threaded onto rod 176) the relative movement that will be permitted between plates 128 and130 can be regulated.

In order to aid persons skilled in the art to better understand myinvention, I :will now explain the operation of it. It will be assumedthat loader 10 is standing still and that the operator desires to moveforwardly in a straight line. In order to accomplish this the operatorneed merely push either one of control handles 32 or 34 forward(clockwise as viewed from the right in FIG. 3). The fur ther forward thecontrol handle is pushed the faster the 'Vehicle will operate. Loader 10will proceed in a straight line because both handles 32 and 34 Will bedisplaced the same amount due to the action of mechanism 126, and sofiuid motors 52 and Will be driving the Wheels on each side of theVehicle at the same speed and in the same direction. If it is nowdesired to change the heading of the Vehicle toward the right theoperator may either move control handle 32 backward relative to handle34 or move control handle 34 forward relative to handle 32. In eitherevent the result is that the Wheels on the left side of the Vehicle willbe driven at a greater speed than the Wheels on the right side so thatthe vehicle will turn toward the right. When the ttun is completed theoperator can release either one of the two control handles and tensionSprings 144 and 146, acting through pins 140 and 142 Will restore plates128 and to identical ,positions, thereby disposing the swash plates ofpumps 50 and 78 in the same position so that the motors will again bedriving their corresponding :Wheels at the same rate of speed. Whileonly the manipulation of control handles 32 and 34 has been explained toaccomplish either straight forward movement or a right hand turnofloader 10, it will be understood that left hand turns, reverse drive orpivoting loader 10 about its centerpoint can be accomplished throughproper manipulation of control handles 32 and 34. In any case, mechanism126 tends to cause conjoint movement of plates 128 and 1130, and hencelike movement of the swash plates of pumps 50 and 78. However, relativemovement of plates 12'8 and 130, and hence displacement of the swashplates of pumps 50 and 78 relative to each other, Can be accomplished bythe operator pushing Or pulling on control handles 3-2 and 34suflicently to overcome the bias of tension springs 144 and 146 with theresult that rods and 142 cock and slide' in their respective slots inplates 128 and 130. The amount of differential movement of plates 128and 130 is limited by the clearance between nuts 178 and the adjacentend of tube 174 of mecharn'sm 172 which connects rods 140 and 142. Ifthe operator has control handles 32 and 34 in any position displacedfrom their normal neutral position and releases them, they are broughtto a predetermined neutral position through the action of spring 168:which bears on cam 162 and Causes rollers '158 and to roll to the apexof the cam. When plates 128 and 130 are brought to this position theswash plates of pumps 50 and 78 which are connected thereto through thelinkage are disposed at Zero displacement so that drive train 36 ofloader 10 is in neutral.

While only a single preferred embodiment has been described in theforegoing detailed description, it is understood that this descriptionis illustrative only and that various changes and modifications can bemade to my invention 'without departing from the spirit and Scope of it.Consequently, the limits of my invention should be determined from theclaims attached hereto.

I claim:

1. For use -with a Vehicle having first and second separate drive means,the combination comprising first means for controlling the first drivemeans, second means for controlling the second drive means, meansinterconnecting said first and second controlling means so thatactuation of one of said controlling means tends to cause Substantiallythe same actuation of the other of said controlling means, saidinterconnecting means being overridable so that said first and secondcontrolling means can be actuated independently of each other, and meansconnected to said interconnecting means for limiting the amount ofindependent actuation of one of said controlling means relative to theother of said controlling means.

2. The combination comprising first and second separate variable outputdrive means, a first rotatable shaft operatively connected to said firstdrive means so that rotation of said first shaft varies the output ofsaid first drive means a second rotatable shaft operatively connected tosaid second drive means so that rotation of said second shaft varies theoutput of said second drive means, interconnecting means connected tosaid shafts so that rotation of one of said shafts tends to causesubstantially the same rotation of the other of said shafts, saidinterconnecting means being overridable so that said shafts Can berotated independently of each other, and means connected to saidinterconnecting means for limiting the amount of independent rotation ofsaid shafts relative to each other.

3. The combination set forth in claim '2 and including means connectedto said interconnecting means for biasing said shafts to a givenposition.

4. The combination as set forth in claim 2 and including a first controlhandle connected to said first shaft and a second control handleconnected to said second shaft.

5. The combination as set forth in claim 2 wherein said interconnectingmeans includes a first plate fixed to said first shaft, a second platefiXed to said second shaft, first and second converging slots in saidfirst plate, third and fourth converging slots in said second plate, afirst rod which extends through and is movable in said first and thirdslots, a second rod wvhich extends through and is movable in said secondand fourth slots, and tension spring means connected between said firstand second rods.

6. The combination as set forth in claim 5 and including first andsecond rollers connected to said first and second plates, respectively,a curved cam engaging said rollers and means biasing said cam againstsaid rollers so that said shafts are biased to a given position.

7. The combination as set forth in claim *5 and including a tube fixedto one of said rods, a third rod extending through said tube and fixedto the other of said first and second rods, and stop means connected tosaid third rod and cooperating with said tube so that rotation of saidshafts relative to each other is limited to a given amount.

8. The combination with a Vehicle having a power train With first andsecond separate variable outputs, mechanism for controlling the powertrain comprising a rotatable sleeve shaft operatively connected. to thepower train to control the first variable output, a second rotatableshaft dsposed to extend through said sleeve shaft and operativelyconnected to the power train to control the second variable output, afirst plate fiXed to said sleeve shaft, a second plate fixed to saidsecond shaft and spaced axially from said sleeve shaft, said first platehaving first and second converging slots therein, said second platehaving third and fourth converging slots therein which register withsaid first and second slots, respectively, a first rod which extendsthrough and is movable in said first and third slots, a second rod whichextends through and is movable in said second and fourth slots, tensionspring means connected between said first and second rods, means forretaining said first and second rods in said slots, a tube fixed to oneof said first and second rods, a third rod fixed to the other of saidfirst and second rods and extending through said tube, stop meansconnected to said third rod so that relative rotation between saidshafts is limited to a predetermined amount, first and second rollersconnected to said first and second plates, respectively, a cam dsposedto engage said rollers and means biasing said cam toward said rollers sothat said shafts are biased to a given position.

References Cited UNITED STATES PATENTS 3,333,485 8/ 1967 Deli et al.74-479 FOREIGN PATENTS 940,56l 10/1963 Great Britain 74-480 MILTONKAUFMAN, Primary Examiner U.S. Cl. X.R.

74--491; ISO-6.48

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3O5,5|9 Dated September 20, l97l InVen Inl m P HeggarL It is Certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column l, line 7l, after 'numercll lO" nserf denofes generally Clcompact Four-wheeled Front end Column 2, line 7l, delete "denofesgenerally a compact four-wheeled front end" Signed and sealed this 19thday of September 1972.

(SEAL) Attest;

ROBERT GOTTSCHALK EDWARD M.FLETCHER,'JR.

Commissioner of Patents Attesting Officer USCOMM-DC O0376-PO9 RM PO-105O0-69) u sl GOVERNMENV PmNTlNG OFFICE inn o-aficfiu

